Molybdenum disulfide (MoS2) belongs to the family of the layered transition metal dichalcogenides (LTMDs). It has been widely used as a dry lubricant and as a catalyst for desulfurization in petroleum refineries. Recently, MoS2 attracted a great deal of attention because of its attractive electronic, optoelectronic, and mechanical properties. In the bulk form, MoS2 is an indirect bandgap semiconductor with an energy gap of ˜1.2 eV. In the monolayer form, MoS2 has a large direct bandgap (˜1.8 eV). Therefore, MoS2 can serve as an important complement to zero-bandgap graphene and enable new semiconductor-related applications of two-dimensional (2-D) materials such as thin-film transistors (TFTs), phototransistors, chemical sensors, integrated circuits (ICs), and thin-film light-emitting diodes (LEDs). As a 2-D nanoelectronic material, MoS2 is advantageous over bulk Si for suppressing the undesirable tunneling between drain and source regions at the scaling limit of transistors and therefore provides benefits for miniaturization of electronic devices beyond Moore's Law. In addition, bulk (or multilayer) MoS2 exhibits relatively high in-plane carrier mobility comparable to that of crystalline Si, as well as robust mechanical and chemical properties, which makes it an attractive material for making flexible electronic devices with high performance and long lifetime.
A broad variety of prototype devices based on few-layer MoS2, such as high-performance field effect transistors (FETs), phototransistors, sensors, and integrated circuits (ICs), have been fabricated and extensively studied in research laboratories. However, the scale-up applications of MoS2, especially the mass production of commercially viable products, demand large arrays of orderly arranged MoS2 structures. This requirement breaks down into two critical challenges in nanomanufacturing, which are (1) incorporating pristine MoS2 films over large areas and (2) patterning MoS2 into ordered micro- and nanostructures over large areas to obtain both desirable electronic properties and required functionality. Several approaches have been attempted to produce MoS2 materials for large area applications, including scotch tape exfoliation, liquid phase exfoliation in an organic solvent, intercalation followed with forced hydration, transition metal sulfurization, thermal decomposition of thiosalts, chemical vapor deposition (CVD), and van der Waals epitaxial growth, etc. So far, a few efforts have been invested to the lithographic patterning of MoS2 sheets and the deposition of MoS2 crystals into ordered arrays. All of these technologies for producing MoS2 structures still suffer from one or more obstacles that prevent the creation of ordered, pristine MoS2 device arrays over large areas. Obviously, an upscalable nanomanufacturing technology capable of producing ordered and pristine few-layer MoS2 patterns would have a transformative impact on future manufacturing of MoS2 electronic and optoelectronic devices and systems.
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